Enhanced Optical Activity by Achiral Rod-Like Molecules Nanosegregated in the B4 Structure of Achiral Bent-Core Molecules

Chirality in a mixture system consisting of bent-core 1,3-phenylene bis[4-(4-8-alkoxyphenyliminomethyl)benzoates] (P8-O-PIMB) and rod-like n-pentyl-cyanobiphenyl (5CB) molecules has been studied. Precise circular dichroism (CD) spectra using thin sample cells indicate mainly two characteristics: (1) the origin of CD signals is due to chiral-segregated bent-core molecules in the B-4 phase, where 5CB is in the isotropic phase; (2) the enhanced CID signal is detected in the B-X phase, where 5CB is in the nematic phase. These results suggest that 5CB molecules are embedded in the network of helical nanofilaments formed by P8-O-PIMB and form helical superstructure with the same handedness as the helical nanofilaments in the B-X phase, resulting in the giant CD signals.